Adjustable valve timing for no control

ABSTRACT

A phase shift mechanism including a plate carrying a pair of oppositely disposed idler sprockets, the plate being pivotally mounted on the crankshaft of an internal combustion engine so that the idler sprockets engage the timing chain at opposite points of its internal periphery and may adjustably control the position of the chain relative to the camshaft and crankshaft by the pivotal movement of the plate on the crankshaft thus effecting phase shifting between the two shafts and changing valve timing relative to piston position.

United States Patent Chadwick ADJUSTABLE VALVE TIMING FOR NO CONTROLInventor: Alexander Chadwick, Farmington,

Mich.

Assignee: Chrysler Corporation,

Park, Mich.

Filed: June 18,1970 Appl. No.: 47,395

Highland US. Cl ..l23/90.l5, 74/395 Int. Cl .Q ..F0ll 1/34 Field ofSearch ..l23/90.15, 90.31; 74/395, 397,

References Cited UNITED STATES PATENTS I i 9/ 1 933 Hemmingsen..123/90.15 X 2/1970 Finlay ..l23/90.l5 9/ 1926 Chisholm ..123/90. 15 Xi 8/ 1931 Duncan l23/90.l5 X

151 3,683,875 451 Aug. 15, 1972 1,871,268 ,8/1932 Hildebrand...l23/90.l5X 2,279,413 4/1942 Read ..'......l23/90.l5 X 3,441,009 4/1969 Rafanelli 1'23/90. l 5

FORElGN PATENTS OR APPLICATIONS $49,175 11/1942 Great Britain ..l23/90KL 760,499 12/1933 Primary Examiner-A1 Lawrence Smith Attorney-Talburttand Baldwin [57] ABSTRACT A phase shift mechanism. including a platecarrying a ,pair ofoppositely disposed idler sprockets, the plate beingpivotally mounted on the crankshaft of an internal combustion engine sothat the idler sprockets engage the timing chain at opposite points ofits internal periphery and may adjustably control the position of thechain relative to the camshaft and crankshaft by the pivotal movement ofthe plate on the crankshaft thus efiecting phase shifting between thetwo shafts and changing valve timing relative to piston position.

2 Claims, 3 Drawing Figures France ..123/9O KL United States Patent 113,683,875 Chadwick [451* Aug. 15, 1972 BACKGROUND This invention relatesto a phase shift mechanism for changing the angular relationship betweencrankshaft and camshaft members while they are in motion. It hasparticular application to the control of emissions in-intemal combustionengines by effecting phase shifting between the crankshaft and camshaftand thus adjusting valve timing relative to piston position.

Workers in the art are already aware of the fact that the certainundesirable components present in engine exhaust can be decreased byproviding certain timing modifications between the combustion chamberintake and exhaust valves.

Specifically, the object of the standard valve timing arrangement is toretain a minimum amount of exhaust in the combustion chamber. This isusually accomplished by arranging for the exhaust valves to close atjust the moment the pistons reach the top of their stroke therebyallowing as much of the exhaust gases as possible to leave thecombustion chambers of the engine.

If the valve timing is modified so as to close the exhaust valves early,that is before the pistons reach the top of their stroke, a certainamount of the exhaust gases are retained in the combustion chamber. Theamount retained can be controlled by adjusting the time at which theexhaust valves are closed. I

When residual exhaust gases are retained by adjusting the valve timing,inter-mixing of the fuel mixture with the residuals occurs in thecombustion chamberv during the subsequent steps of the combustion cycle.It has been demonstrated that such inter-mixing reduces the amount ofcarbon monoxide and unburned hydrocarbons in the exhaust. Moreimportantly, it retards the formation of the oxides of nitrogen (N Sincethe amount of undesirable exhaust constituents produced vary with thespeed of the engine, it is important that a valve timing arrangement forretaining residual exhaust gases be dynamic. That is, it should becapable of effecting adjustable variations in the valve timing while theengine is in operation and during different speeds.

Several adjustably variable valve timing arrangements have beensuggested in the prior art to provide efficient engine operation atdifferent speeds. However, none of these have been as readilyincorporated into production engines as the arrangement disclosedherein.

SUMMARY OF THE INVENTION This invention has as its primary object theprovision of a simplified mechanical arrangement for dynamically varyingthe rotational position between the camshaft and crankshaft in order toadjust valve timing. The purpose is to control the retention of residualexhaust gases in the combustion chambers of the engine and to therebyreduce the amount of certain constituents in the exhaust, particularlythe amount of the nitrous oxides (N0 These and other objects areattained by providing a pair of idler sprockets on pivotally mountedsupport means which horizontally positions the sprockets between thecrankshaft and camshaft whereby the valve operating times may be changedby the movement of the valve operating shaft or camshaft relative to thecrankshaft when the support means is pivoted to move the sprocketsrelative to the chain. The support means comprises a plate pivoted fromthe crankshaft axis, the plate including a geared portion. A controlgear, rotatably controlled bythe throttle for example, engages thegeared portion of the support plate to control plate position. Themechanism is operable while the engine is running to provide dynamicphase variation.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an end view of an internalcombustion engine including a phase control or phase shift mechanism bymeans of which the rotational relationship between the camshaft andcrankshaft and thus justably controlling its position according to theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring specifically to FIGS.1 and 2, an engine 10 is shown which includes a crankshaft 12 carrying acranlmhaft gear 14 and a camshaft 16 carrying a camshaft gear 18. Gears16 and l8are connected by timing chain 20 such that rotation ofcrankshaft 12 causes the simultaneous rotation of camshaft 16.

A phase shift mechanism generally indicated by numeral 22 is positionedintermediate gears 14 and 16 at at least partially within the peripheryof timing chain 20. The mechanism comprises support means such as plate24 on which two oppositely disposed idler sprockets 26 and28 are carriedin a position to engage chain 20 internally of its periphery as shown inFIG. 1. Plate 24 is pivotally disposed about the axis of crankshaft 12by being mounted thereon.

Crankshaft gear 14 bears a fixed rotational relationship with crankshaft12 on which it is fixedly mounted and thus its operation and position isdirectly related to piston position. Likewise, camshaft gear 16 bears afixed rotational relationship with camshaft gear 18 on which it isfixedly mounted and thus its operation and position is directly relatedto valve position.

Usually, timing chain 20 provides a fixed rotational relationshipbetween gears 14 and 18 and thus between shafts 12 and 16 and ultimatelybetween the piston and valve positions. However, in the engine shown inFIGS.

. 1 and 2 this is not the case. Pivo'tally mounted phase shift plate 24provides a dynamic and adjustable or variable rotational relationshipbetween crankshaft 12 and camshaft 16.

The rotational relationship or phase is determined by the pivotalposition of plate 24 on. crankshaft 16. FIG. 1, by means of the solidlines, shows plate 24 in the operating position it would assume when theengine is operating at full load. As indicated by the horizontalposition of the top of plate 24 and sprockets 26 and 28,

at full engine load crankshaft and camshaft gears 14 and 16 are rotatingin a given phase relationship whereby the valves and pistons (not shown)ofthe engine are operated in a predetermined sychronized relationship asis well established in the art.-

As the load decreases, plate 24 may be pivoted to a different positionas shown in phantom. This change causes a positional change in theangular relationship between chain 20 and gears 14 and 18 due to thechange in tension exerted by each of the sprockets 26 and 28 againstchain 20. The decrease in distance between sprocket 28 and gear 14' andbetween sprocket 28 and gear 18 and the increase in distance betweensprocket 26 and gears 14 and 18 result in re-adjustment of chain 20 andthe rotation of gear 18 out of phase relative to gear 14.

The phase relationship between gears 14 and 18 is thereby shifted to onein which camshaft gear 18 lags behind crankshaft gear 14 slightlywhereby the engine valves operate at a different time relative to theposition of the pistons. Specifically, the lag causes the early closingof the exhaust valves and the retention of additional residual exhaustgas in the combustion chamber. Pivotal movement of plate 24 in theopposite direction will of course have the opposite effect.

The position of plate 24 is controlled by the arrangement shown in FIG.3. Plate 24 is shaped to include a geared portion or ear 30. A rotatablecontrol gear 32 engages portion 30 and may be rotated while the engineis running to adjust the position of plate 24 and thus vary theoperating time of the valves.

Gear 32 may be controlled by the accelerator pedal position as indicatedin FIG. 3'. However, it is possible to use other functions or schedulesif desired such as, engine speed,.car speed, and the like.

The embodiments of the invention in which an exclusive property or rightis claimed are defined as follows:

1. In an internal combustion engine, the combination with a camshaft, acrankshaft and a drive chain connecting the shafts, of a pair of idlersprockets for engaging the chain and a pivotally mounted support meanscarrying the idler sprockets and positioning them against the insideperiphery of the chain at generally opposite points whereby therotational relationship between the shafts may be varied by pivoting thesupport means and changing the relative tension exerted by the sprocketsagainst the chain, the improvement wherein the support means comprises asingle body pivotally mounted on the crankshaft and carrying bothsprockets thereon, the support body including a geared portion, thecombination further including a control gear for controlling theposition of the support body, the control gear being rotatably carriedby the engine to engage the geared portion on the support body wherebyrotation of the control gear causes the support body to pivot on thecrankshaft and change the position of idler sprockets.

2. The combination according to claim 1 wherein the control gear isoperably connected to the engine accelerator.

1. In an internal combustion engine, the combination with a camshaft, acrankshaft and a drive chain connecting the shafts, of a pair of idlersprockets for engaging the chain and a pivotally mounted support meanscarrying the idler sprockets and positioning them against the insideperiphery of the chain at generally opposite points whereby therotational relationship between the shafts may be varied by pivoting thesupport means and changing the relative tension exerted by the sprocketsagainst the chain, the improvement wherein the support means comprises asingle body pivotally mounted on the crankshaft and carrying bothsprockets thereon, the support body including a geared portion, thecombination further including a control gear for controlling theposition of the support body, the control gear being rotatably carriedby the engine to engage the geared portion on the support body wherebyrotation of the control gear causes the support body to pivot on thecrankshaft and change the position of idler sprockets.
 2. Thecombination according to claim 1 wherein the control gear is operablyconnected to the engine accelerator.